Chief Delphi - Which sensors should be used throughout the robot?

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Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Technical Discussion (http://www.chiefdelphi.com/forums/forumdisplay.php?f=22)

- - Which sensors should be used throughout the robot? (http://www.chiefdelphi.com/forums/showthread.php?t=137836)

mman1506

26-07-2015 17:56

Re: Which sensors should be used throughout the robot?

I really love the allen-bradley photosensors from 2011 KOP. They come in super handy for indexing of game pieces, rpm measurement, elevator indexing (homing). The square body and threaded barrel make them easy to mount and they do a great job at rejecting IR light interference from the field lights.

We also had a good experience with the AMT10-V encoder this year. The CPR of the encoder can be adjusted via on-board dip switches and they can be mounted on shafts from 2-8 mm (1/4",3/16",1/8") making them exceptionally versatile. At $23 a piece we can keep lots spares around.

Abhishek R

26-07-2015 18:36

Re: Which sensors should be used throughout the robot?

I don't know what brand/model specifically we use, but:

Drivetrain - Encoders
Elevator - Combination of Encoder and String Potentiometer, as well as Limit Switches to detect the ends and to zero/calibrate
Flywheels - IR/Photo Sensors
Proximity (detecting whether there is a tote/can in the robot or not) - Ultrasonic and/or IR/Photo Sensors

We also used a Limit Switch last year to determine when our catapult had returned to its starting position. The most common sensor we use is definitely IR/Photo (other than the encoders on the drivetrain) because they're so versatile.

thatprogrammer

26-07-2015 18:51

Re: Which sensors should be used throughout the robot?

What ir sensors would everyone reccomend? Same question for retroflective sensors.

I assume any sensor that's digital and merely returns a boolean value can be programmed the same as a limit switch?

Gregor

26-07-2015 19:44

Re: Which sensors should be used throughout the robot?

http://m.ebay.com/itm/190892864042?_mwBanner=1

These are from China and take absolutly forever to ship, but if you stock up on them now they're great to have, especially given the price.

We used them everywhere this year, two to sense totes, two to sense the tape on the floor for our 3 tote, and one to sense a container. Last year we used it to sense the limit on our catapult. Just don't be foolish like us and point two towards each other to try and sense the totes, you'll end up bending a sensor mount up so they don't interfere. :rolleyes:

http://www.wcproducts.net/sensors

I also love these made for FRC sensors, thanks 971! We used them as the upper and lower limits for our elevator. Put velcro on the sensor and a 1/8 rivet on the magnet and you have an easily adjustable, great sensor.

Between these two sensors we've totally eliminated our use of pesky limit switches. I love their price and their ease of use.

thatprogrammer

26-07-2015 19:48

Re: Which sensors should be used throughout the robot?

Quote:

Originally Posted by Gregor (Post 1491357)

Our school is unlikely to allow us to buy stuff through ebay. Any similar sensors from a more official website? Thanks!

AdamHeard

26-07-2015 19:56

Re: Which sensors should be used throughout the robot?

Have you tried them for a flywheel?

Quote:

Originally Posted by Gregor (Post 1491357)

http://m.ebay.ca/itm/251609690366?_mwBanner=1

These are from China and take absolutly forever to ship, but if you stock up on them now they're great to have, especially given the price.

We used them everywhere this year, two to sense totes, two to sense the tape on the floor for our 3 tote, and one to sense a container. Last year we used it to sense the limit on our catapult. Just don't be foolish like us and point two towards each other to try and sense the totes, you'll end up bending a sensor mount up so they don't interfere. :rolleyes:

http://www.wcproducts.net/sensors

I also love these made for FRC sensors, thanks 971! We used them as the upper and lower limits for our elevator. Put velcro on the sensor and a 1/8 rivet on the magnet and you have an easily adjustable, great sensor.

Between these two sensors we've totally eliminated our use of pesky limit switches. I love their price and their ease of use.

Gregor

26-07-2015 20:00

Re: Which sensors should be used throughout the robot?

Quote:

Originally Posted by AdamHeard (Post 1491359)

Have you tried them for a flywheel?

No.

Necroterra

26-07-2015 20:00

Re: Which sensors should be used throughout the robot?

Quote:

Originally Posted by thatprogrammer (Post 1491329)

How exactly are the reed switches programmed? Same as limit switches?

I see people already let you know that you can use these magnetic reed switches as a standard DigitalInput, or set it up as the Limit Switch on a TalonSRX, but there's a few others. The class Counter can be used as such:

Code:

Counter reedSwitchWatcher = new Counter(channel)

Code:

Counter reedSwitchWatcher = new Counter(digitalInput)

As well as a few others. This tells the FGPA to directly watch the digitalInput and count when it is active / rising edges / falling edges / whatever you set it to. This means you don't have to check the switch as often as you would if you were accessing it directly, and you can use it to act on a switch's activation much more precisely.

There is also an Interrupt system built into the processor, but I never used it. From what I understand, it's essentially an event handler which executes a function handler when a DigitalInput is fired.

mman1506

26-07-2015 20:05

Re: Which sensors should be used throughout the robot?

Quote:

Originally Posted by thatprogrammer (Post 1491358)

Our school is unlikely to allow us to buy stuff through ebay. Any similar sensors from a more official website? Thanks!

http://www.amazon.com/6-36V-Photoele...lectric+sensor

thatprogrammer

26-07-2015 20:14

Re: Which sensors should be used throughout the robot?

Here is a basic chart of what I've come up with so far, based on responses in this thread:

Code:

Arms: Potentiometer or Encoder -> Hard to zero(?)

Elevator: Encoder

Flywheel: IR or photoelectric sensor (Hoping to find some good options for this, a bit scared of using the cheap sensor on high rpm flywheels)

Stops: Hall effect.

Intakes/Hoppers: IR

mman1506

26-07-2015 20:17

Re: Which sensors should be used throughout the robot?

Quote:

Originally Posted by Gregor (Post 1491357)

http://www.wcproducts.net/sensors

I also love these made for FRC sensors, thanks 971! We used them as the upper and lower limits for our elevator. Put velcro on the sensor and a 1/8 rivet on the magnet and you have an easily adjustable, great sensor.

Between these two sensors we've totally eliminated our use of pesky limit switches. I love their price and their ease of use.

A cheaper more durable alternative to the 971 WCP sensor are these inductive proximity sensors.
http://www.ebay.ca/itm/New-LJ12A3-4-...em338fe7 6170

Since they are inductive instead of magnetic they can be triggered by anything ferrous like a steel rivet.

There are also magnetic hall effect versions http://www.ebay.ca/itm/Hall-Effect-H...em487c2a 613c

marshall

26-07-2015 20:39

Re: Which sensors should be used throughout the robot?

Quote:

Originally Posted by mman1506 (Post 1491365)

Alternate Amazon links for those in need:

http://www.amazon.com/Effect-Sensor-...y+Switc h+NPN

http://www.amazon.com/Amico-DC6-36V-...J12A3-4-Z%2FBX

AdamHeard

27-07-2015 00:37

Re: Which sensors should be used throughout the robot?

After accidentally posting in battlebots thread...

We used these Chinese encoders in place of S4's for practice bots to save some money.

They're way bigger, but worked well for us. Took about two weeks to get to us.

Max Boord

27-07-2015 01:01

Re: Which sensors should be used throughout the robot?

Quote:

Originally Posted by thatprogrammer (Post 1491364)

Here is a basic chart of what I've come up with so far, based on responses in this thread:
Arms: Potentiometer or Encoder -> Hard to zero(?)
Elevator: Encoder
Flywheel: IR or photoelectric sensor (Hoping to find some good options for this, a bit scared of using the cheap sensor on high rpm flywheels)
Stops: Hall effect.
Intakes/Hoppers: IR

Arms: Potentiometer. Encoders have to be zeroed every time the robot boots up which can be a problem if the arm starts in a different position in each match.
Elevator: String Potentiometer. They output a value directly proportional to lift height. This is how 1065 measured our lift height this season.
Flywheel: Optical. Encoders produce too much information for this and caused problems for us in 2013 before we switched to optical measurement on our shooter.
Stops: Hall effect/ Optical. They don't break like limit switches do. We used them as a backup to our string potentiometer this year to prevent from hitting hard stops. They output a solid state signal and some have a 3rd "reversed output" wire.
Hoppers: Limit switches or optical.
Drive: Encoders for distance, Gyro for orientation. Use 2 gyros 1 upside down positioned above or below to account for gyro drift. Make sure the driver can zero it if the gyros are used for field oriented omni drive.

Thad House

27-07-2015 01:50

Re: Which sensors should be used throughout the robot?

Quote:

Originally Posted by Max Boord (Post 1491411)

String pots work well for a game like this year, but most years they are not a good option. Most elevator games need more then 50 inches of travel, which was the longest we could find. It also cost more then $200 just for 1 50 inch one. An encoder is a much cheaper option, and your only option in budget if you need more then 50 inches of travel.

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